The present invention relates to grafts implantable to bypass an obstruction or other undesirable condition within a vessel or other tubular organ, and more particularly to systems for deploying such grafts and fixation elements for securing them.
Bypass grafts are particularly useful in treating vascular diseases, but have other applications including treatment of urinary incontinence, infertility, and gastrointestinal defects such as occlusions and ulcers. Stenosed vessels cause ischemia which potentially leads to tissue infarction. Conventional techniques to treat partially occluded vessels include balloon angioplasty, stent deployment, and surgery to attach a graft to bypass the stenosed lesion. Surgical implantation of a bypass graft typically requires performing a thoracotomy, placing the patient on a cardiopulmonary bypass system, and using cardioplegia to induce cardiac arrest. This permits a suturing of the graft between cardiac vessels without the risk of excess blood loss or the need to accommodate motion of the heart. Less invasive attempts at positioning bypass grafts involve a thoracostomy to produce a conduit to the stenosed lesion. This approach uses endoscopic visualization to position the graft. The delivery for such graft requires modified surgical instruments (e.g., clamps, scissors, scalpels, etc.) and further involves ports inserted through small (approximately one inch) incisions to provide access into the thoracic cavity.
There remains a need for a minimally invasive technique for deploying and securing a bypass graft, and for a fixation means for more reliably securing a graft without the need to suture the graft.
Accordingly, it is an object of the present invention to provide a system for translumenal deployment of a bypass graft.
Another object is to provide a more effective fixation means for securing a deployed bypass graft.
A further object is to provide a system for bypass graft deployment, in which features incorporated within the graft reduce the time and difficulty of deployment.
Yet another object is to provide an improved process for deploying and securing grafts along body lumens to bypass obstructions and other undesirable features within the lumens.
To achieve these and other objects, there is provided a body implantable graft. The graft includes a tubular graft wall having opposite first and second open ends. The graft defines a fluid flow lumen between these ends. The tubular graft is adapted for a selected placement with the first end at a first location in body tissue and the second end at a second location in body tissue, to provide a fluid flow path between the first and second locations to bypass an obstruction between those locations. The graft also includes a graft fixation mechanism operable to heat the graft wall at least near the first end following placement, to thermally secure the graft wall and adjacent tissue.
The preferred fixation apparatus is an electrically conductive heating element mounted to the graft wall near the first end. The element can be annular, and may incorporate a feature to mechanically secure the graft, e.g., a collet or a grommet.
In similar fashion an electrically conductive heating element or other fixation apparatus can be used to secure the second end of the graft at the second location. The heating elements can be coupled to an RF power source and used in conjunction with an indifferent electrode, to secure the graft by ohmic heating.
Another aspect of the invention is a system for deploying a bypass graft. The system includes an elongate and flexible carrier having a proximal end and a distal end. The carrier is insertable by the distal end for intralumenal movement toward a selected site along a body lumen while the proximal end remains outside the body. A tissue perforating mechanism, near the distal end of the carrier, is positionable at a first location near the selected site, and operable from the proximal end of the carrier to form a first opening through tissue at the first location. Further, the mechanism is positionable at a second location near the selected site and operable to form a second opening through tissue at the second location. An elongate graft guide, supported by the carrier and disposed near the distal end, is movable into a guiding position in which the guide extends from the first location through the first opening to the second location and through the second opening. The system further includes a tubular graft adapted to be mounted to the carrier for movement along the carrier. A graft controller is operable to move the graft distally along the carrier toward the graft guide, and then distally along the graft guide when the guide is in the guiding position, to a bypass location in which the graft extends from the first location to the second location and also extends through the first and second openings.
The preferred carrier is a catheter having a catheter lumen. An elongate dilator is contained slideably within the lumen, and has a tapered distal tip. An elongate needle is slideably contained within the dilator.
According to one embodiment, the dilator provides the graft guide, while the tissue perforating mechanism includes the needle and the distal tip of the dilator.
According to another embodiment, a distal end region of the catheter provides the graft guide. The dilator and needle are used to perforate and dilate tissue to form the first and second openings. The dilator is not used to guide the graft, but is used to guide the catheter, particularly the distal end region which in turn is used for positioning the graft after withdrawal of the dilator.
According to another aspect of the present invention, an alternative system is provided for implanting a bypass graft without the need for a catheter. This system includes a tissue dilating member having at its distal end a tissue dilating tip converging in the distal direction. A tissue puncturing tool is supported within the dilating member and extends in the distal direction from the dilating tip. The tool is adapted to puncture or perforate a tissue wall to form an orifice enlargeable by the dilating tip. The system includes a graft with a substantially fluid impervious graft wall. First, second and third openings are formed through the graft wall at first, second and third spaced-apart regions of the wall, respectively. The graft is adapted for a removable mounting on the dilating member in which the dilating member extends through the first and third openings, with the first opening near the dilating tip and the third opening proximally of the first opening. This enables use of the dilating member to insert the first region of the graft wall into a first orifice in the tissue wall, for fixation of the first region in the first orifice. The graft further is slideable relative to the dilating member to permit a proximal withdrawal of the dilating member from the first region after its fixation, and further to allow an insertion of the dilating member into the second opening for securing the second region of the graft wall within a second orifice in the tissue wall. As a result, the graft provides a fluid flow conduit between the first orifice and the second orifice. A closure mechanism is provided for closing the third opening, following withdrawal of the dilating member from the graft, after the first and second regions have been secured.
Another aspect of the present invention is a process for translumenally deploying a bypass graft, including the following steps:
a. advancing an elongate catheter intralumenally toward a selected site along a body lumen;
b. with a distal end of the catheter near the selected site, using a tissue perforating mechanism mounted near a distal end of the catheter to form a first opening through a tissue wall defining the body lumen;
c. advancing tissue perforating mechanism through the first opening, and then to a selected location spaced apart from the first opening, then using the mechanism to form a second opening through tissue at the selected location;
d. advancing a graft guide through the first opening, distally to the selected location, then through the second opening;
e. with the graft guide so positioned, advancing a tubular graft along the guide to a bypass location in which the graft extends from the first opening to the second opening and through the first and second openings, thus to form a bypass conduit in fluid communication with the body lumen; and
f. while maintaining the graft in the bypass location, proximally withdrawing the catheter, the tissue perforation mechanism and the graft guide.
Thus, in accordance with the present invention, bypass grafts are deployed more easily using techniques that are considerably less invasive, and upon deployment are more reliably secured.